Push-in type terminal unit for lamp receptacles



United States Patent PUSH-IN TYPE TERMINAL UNIT FOR LAMP RECEPTACLESVictor R. Despard, Syracuse, N. Y., assignor to Pass & Seymour, Inc.,Syracuse, N. Y., a corporation of New York Application June 25, 1954,Serial No. 439,280

9 Claims. (Cl. 339-95) This invention relates to electric wiring devicesand more particularly to connecting, continuing and terminatingapparatus for use therewith.

It is a general object of the present invention to provide novel andimproved devices of the type described having unique circuit connecting,continuing and terminating apparatus associated therewith.

More particularly it is an object of the present invention to provide anovel and improved electric fixture or lamp receptacle of the ceramictype'for mounting as a box cover and having littings including automaticwire gripping terminals and lamp base contacting tongues.

An important object of the present invention resides in the unitaryconstruction of each of the duplicate littings whereby it includes as anintegral unit a pair of similar wire grippings spring terminals adaptedto automatically engage and hold a bared wire end inserted therein, anda tongue adapted to act as a lamp base contact engaging element.

Another important object of the invention consists in .providing on eachfitting a wire gripping spring terminal of the short open-ended slottype wherein integral means areprovided to prevent misalignment of thetwo wings of the wire grip to insure holding under all conditions andalso to prevent the possibility of wing collapse or wire end cutting onexcessive tension on the wire.

A further object ofthe invention resides in the provision of a unitiitting which combines two laterally spaced, automatic, spring type,wire grippers connected flexibly to each other through a looped strapwhich carries the socket terminal, whereby each gripper assumes itsproper relationship to the supporting and side restraining walls of theinsulation base.

A still further object of the invention consists in the provision of aspring type Wire gripper of extreme shortness achieved by connecting thegripping wings together at one end only, restraining the wing side edgesin the insulation and providing integral supports on the free ends ofthe wings to resist collapse on wire withdrawal tension.

Other and further objects and features of the invention will be moreapparent to those skilled in the art upon a consideration oftheaccompanying drawing and following specification wherein is disclosed asingle exemplary embodiment of the invention with the understanding thatsuch changes and modifications may be made therein as fall within thescope of the appended claims without departing from the spirit of theinvention.

In said drawings:

Fig. l is a fragmentary rear elevation of a wiring device incorporatingthe features of the present invention shown with the rearinsulation'cover plate and one of the connector-terminal fittingsremoved to illustrate the contiguration of the insulating base forcooperation therewith;

FigA 2 is a section taken on the plane indicated by line 2`2 of Fig- 1;

Fi'g- 3` is a fragmentary section taken on the plane of line 3-3 in Fig.1 and illustrating the cooperation of the 2,748,363 Patented May 29,1956 wire gripper wings with the side wa'll of their receiving slot; andg Fig. 4 is a view of a connector-terminal fitting unit beforeinstallation, looking from the inner or open end and illustrating thecollapse preventing feet on the wing ends.

In my copending application Serial No. 378,380, for Convenience Outletwith Improved Wire and Plug Blade Gripping Means, tiled September 3,.1953, there is disclosed terminal means for quickly and automaticallyconnecting conductors to electrical wiring devices of the house and oicebuilding type, where the bared end of each conductor wire is held byspring gripping means, instantly providing both for mechanical andelectrical connection between the conductor and the electrical parts ofthe apparatus to which it is to be connected by the simple operation ofinserting the end of the conductor through an opening in the back Wallof a wiring device andpushing it in for a short distance. Thatparticular disclosure involved a dual convenience outlet and permittedthe 'elongated construction ofthe wire gripping mechanism with thelongitudinally disposed wire engaging slot closed at both ends by metalportions integral with the deilectable wings spaced apart less than thethickness of the wire to be engaged. The closing of both ends of thisslot imparted a rigidity to the connector unit which is not possible ina shorter unit such as is required in certain other types of wiringdevices. It is therefore the purpose of the present invention to providea short type of wiring-unit, spring-wing, connector of the open end typeand to pro vide thereon means to compensate for the lack of slot closureat one end so that the operation is the full equal to that disclosed inthe earlier application.

Referring now to the drawing, it will be seen that the invention isembodied in the conductor and adjacent insulation parts of a wiringdevice usually referred to as the box cover type, i. e., it is aporcelain or plastic molded lamp holder or receptacle somewhat greaterin diameter than the usual 3% or 4 inch wiring box and may besubstituted for the common metal cover thereof, thus providing an outletfor a light at the box in addition to what other functions the box mayperform in housing the junctions of other conductors in the wiringsystem.

For the purpose of covering such a box the wiring device is composed ofa base 10 having a somewhat greater diameter than the box and having anintegral central extension 11 provided with an axial well 12 for thereception of the screw base of a conventional incandescent lamp. In thepresent construction the circular walls of' the Well 12 are providedwith a molded thread 13 for cooperating with the threads of the lampwhich screws directly into the well. In the rear face of the base 1li,which is hollow in various places for the sake of lightness, there is alarge central hollow 14, generally rectangular in form, as seen in Fig.l, and composed of a plurality of irregular smaller depressions ofvarying depths. This hollow is adapted to be covered, as seen in Fig. 2,by a closure plate 15 of some rigid, insulating plastic material ofvonly sufficient thickness to provide the'necessary strength forretaining the conductor parts in position, as will later appear. Thiscover plate is arranged to bear on the central platform 16 dividing thehollow into two major areas and itself being only lower than the planeof the border 17 around the hollow by the thickness of the plate 15.This platform and shelves 18 at the ends of the hollow provide forsustaining the cover while to insure proper orientation the extensions19 and 20 of the shelves have different widths to accommodatecorrespondingly sized tongues on the two ends of the cover plate. Thecover plate is secured in position in any satisfactory manner, as byscrews 21, suitably engaged in the material of the base.

On each side of the central platform 16 is an electrical fitting unit24, the two being identical, so that only one will be described. One" isshown in position at the right in Fig. 1 while at the left theinsulation is exposed to permit consideration of the shapes of thevarious compenent parts of the depressions in the base.

Each fitting, which may be defined as a duplex wire gripping and lampbase contacting device, is composed of a unitary punching or stamping ofspring material of good conductivity such as high grade or Phosphorbronze. It is shaped from a single piece of sheet metal to the formillustrated in the several figures. Thus looking at Fig. l there are twowire gripper sections 25, 26 of similar construction, each rectangularin plan and joined by a lateral neck 27 near the outer end of its inneredge to one arm 28 of a strap-like loopv or bight which extends towardvthe center of the base until it meets the edge of the platform 16 whenit is turned down as parts 29, seen in Figs. 2 and 3. These two parts 29join each other and merge into the elongated narrow tongue 30,preferably having a stud 31 pressed into the outer end.

The downturned portion 29, 29 of the loop is accommodated loosely inchannel 32 extending in an axial direction into the base toward thefront and adjacent the widened center portion of platform 16. It extendsinto well 12 through the narrower and thinner slot 33 for the tongue andis positioned to cause it to enter against the circular wall of thewell. Thus the tongue on each fitting extends for a substantial distanceinto the receptacle for the lamp base, and the one intended to engagethe screw shell of the base is received in a channel or groove 34through the threads 13 for the purpose. The stud and outer end of thistongue are sprung inwardly so that the stud is insured of contact in thebottom of the threads of the lamp base screw shell as it is inserted inthe receptacle. The other tongue, after insertion, is bent ldownwardlysharply over the edge of its slot 33 so as to lie along. and slightlysprung up from the bottom with the stud projecting outwardly to engagethe center contact of the lamp base. Thus the two idenical fittingsprovide for the screw shell and central contacts of the lamp socket andthe loops or bights formed of the parts 2S, 29, 29, 28 and theirextensions 27 to the wire grippers 2S provide for a very tiexibleresilient connectien between these grippers so that each is permitted tofloat in its own recess portion and assume the required positions as theresult of the use to which it is being put. The connecting parts offersubstantially no restraint to this.

The recess portions allocated to the individual wire grippers are seenat 35 in Figs. 1, 2 and 3 and are indented longitudinally into platform16, have parallel sides 36, rectangular inner ends 37 and a pointedopposite end 38. They are of considerable depth at the size of theirtops and then the sides taper to the narrow bottom 39. Each pair ofrecesses 35 open from the bottom of a larger one 40 which lowers thefitting below the cover 15.

To understand the purpose of the shape of opening 35 consideration mustbe given to the construction and operation of the wire gripper. Each iscomposed of two parallel strips or wings 42 attached only by one oftheir ends to the at part 43 of the tting extending alongy its outeredge. This part 43 is provided with an upturned flange 44 for its fulllength, as seen in Figs. l, 2 and 4. This part therefore hasconsiderable stiffness. The wings 42 are spaced for the greater part oftheirV length and at their outer ends by the slo-t 45 of less width thanthe thickness of the smallest wire to be used and gripped by the device,but this slot widens out to the opening 46 at the inner ends of thewings, narrowing the width of the wings to give them added resilience inrespect to their base portion 43. Each wing is deected or bent to lowerthe edges of the slot 45 below the general plane of the fitting and asfar as possible this is done without changing the wings from planesurfaces except at the areas of intieetion adjacent the portion 46 ofthe slot. These wings'in their plane form are clearly seen in Fig. 3 andthe inflection areas where they merge with the area 43 are also visiblein this figure.

The ends of the gripper wings 42 are narrowed as at 47 and bent upwardly90 to provide the tips or feet 48, seen in elevation in Fig. 4. Theirends are cut off parallel to the general upper surface of the fitting atslightly less height than that of the ange 44.

The depressions 35 have their side walls 36 extending for a shortdistance at right angles to the plane of the base, as seen in Fig. 3, sothat the outer edges of gripper tongues 42 can closely engage themwhereby the wings are prevented from spreading when a wire is insertedinto the funnel-like entrance section presented by them, as seen in Fig.3. These same edges of the blades engage the sloping wall 50 mergingwith walls 36 to support the wings during wire insertion.

The two fittings are held in position by the cover plate 15 whichengages against the upper edges of their flanges 44, as seen in Fig. 2,the depressions 40 being sufficiently deep for that purpose as alsorevealed in that figure. The areas 43 adjacent the anges are seenresting on holsters 51 adjacent the ends of the depressions 35 tofurther hold the blades in position. The sloping walls of thesedepressions 35, indicated by the reference characters 50, haveconsiderably greater included angles than between the wings so thatthese are never prevented from exing to the degree necessary to grip anysize wire.

The cover plate 15 has a hole through it at 54 directly above the slot45 between the wings of each fitting and near the outer end thereof andsized to receive any of the usual conductor wires used in householdwiring, i. e. from size 16 to size l2, and the bared end of one of thesemay be pressed through the hole and pushed between the wings, flexingthem to spread the slot. The end of the wire is received in and itsmovement stopped by the bottom of the tapered circular well 55 justbeneath the hole 54.

It will be seen that the action of pressing a wire through the slotbetween the wings cannot spread them laterally because of theirengagement with the walls 38 of the recess in which they are housed, andthey must be thereby constrained to rotate in opposite directions abouttheir outer edges as fulcra to open the gap for the insertion of thewire, increasing the flexing where they are joined to the part 43 of thefitting. Any effort to withdraw the wire only tends to close the slotand cause the wing edges to grip more tightly. It is, however, highlyimportant that the inner edges of the wings be maintained in alignmentfor otherwise the wire might be released by widening of the slot bydisplacement of one wing in respect to the other. Moreover they shouldnot be permitted to be drawn too tightly together by withdrawal tensionon the wire for fear of cutting the latter. The feet 48, referred toheretofore, serve the dual purpose of preventing misalignment andpreventing wire cutting, since on the slightest withdrawal tension theyare drawn to and engage the inner face of the cover plate 15 andmaintain the ends of the wings in alignment. The feet have flat ends,which engagey the cover and. prevent the wings from rotating toward eachother to such an extent as to achieve a cutting position.

In the event that it should be desired to release a conductor held bythe spring wings of a gripper, a second opening 56 isv provided in thecover plate adjacent the inner end' of each slot 45 into which anappropriate tool may be inserted to force the slot wider and' thusrelease the conductor. If such a tool is of. steel it will be ofsutiicient hardness not to be gripped like the copper conductor and canthus be withdrawn. It is' convenient if this opening 56- is a transverseslot to receivethe tip of a knife blade since the taper of the endl ofthe bladefacilitates the opening of the slot and the later withdrawal ofthe tool after the wire is released.

Two grippers are provided on each fitting unit since in many cases it isdesired not only to connect the wiring device into the electrical systembut to provide for continuing the circuit and the added terminal on eachfitting provides for this in an extremely simple manner. In addition itpermits a balanced and symmetrical construction of the ttings which areidentical and can hence be manufactured from the same die.

I claim:

l. A push-in type wire gripping terminal for electric wiring devicescomprising in combination, a base of insulating material having adepression therein, a sheet metal wire gripper comprising wings withspaced parallel adjacent edges and cach having one end attached to aconductor strap, the opposite ends of said wings being free and eachhaving a foot normal thereto, said wings being inclined laterally andoppositely to guide a wire end into the slot between and spacing saidwings, the outer edges of said wings being confined against lateralspreading by engaging the walls of said depression below the surface ofthe said base, and a cover for said base adapted .to hold the saidgripper in position thereon, said cover having an opening therein forthe entrance of a wire into said slot, said wing feet substantiallyengaging said cover to prevent misalignment of the wings or wire cutoffon excessive withdrawal tension.

2. Electric wiring apparatus of the type described having incombination, an electrical contact, means for connecting an electricalconductor wire to said contact comprising a strip of resilient metalextending from said contact having outer longitudinal edges and alongitudinal slit midway between them forming spaced flat wings havingfree and attached ends, the attached ends of the wings being oppositelytwisted to incline the wings out of the plane of the strip to guide theend of a bared wire into the slit, means acting adjacent said free endsto hold the edges of the slit in alignment when tension is applied tothe wire and rigid means engaging the said outer longitudinal edges toprevent lateral spreading of the wings.

3. Electric wiring apparatus of the type described having incombination, an insulating housing having a body and a back cover, anelectric contact in said body, means for connecting an electricconductor wire to said contact comprising a strip of resilient conductormetal end-connected to said Contact, supported by said body and havingan open ended longitudinal slot therein bordered by wings inclinedoppositely from the strip outer edges and yieldable to accept the baredend of a conductor wire through the slot between the wings to be grippedby the wing edges to resist withdrawal, the cover having a wire openingtherein in alignment with the slot to direct the bared end of the wireinto the slot, the body having vertical walls engaging said outer edgesto prevent the wings spreading laterally and the free ends of the wingshaving feet normally substantially engaging said cover to maintain slotedge alignment when the inserted wire is tensioned.

4. In a box cover type of lamp receptacle, in combination, a mouldedbase having a lamp base receiving shell integral with and extending fromthe front face thereof, moulded lamp engaging threads in said shellhaving a longitudinal groove therethrough, a large hollow in the backface of the base opposite said shell, diametrically opposite passagesthrough said base from the bottom of the shell to the hollow, oneforming an extension of said groove, a separate extension of said hollowadjacent and communicating with each of said passages, duplicatefittings one in each extension and each having integral therewith; acontact tongue extending through its passage and into the receptacle, apair of laterally spaced wire gripping devices and a flexible strapconnecting said grippers together and to said contact tongue; and acover closing said hollow, secured to said base and engaging and holdingsaid fittings in position.

5. The device in claim 4 in which each wire gripping device comprises arectangle of sheet metal having an upturned flange at one end and alongitudinal slot normal thereto and bisecting most of the remainderthereof, forming wings, said slot being widened at its inner end and thewings being twisted adjacent said widened portion to form a trough forguiding a conductor wire into said slot.

6. The device of claim 5 in which the said flanges are engaged by saidcover to hold the fittings in position.

7. The device of claim 6 in which the free ends of said tongues havefeet extending parallel to said llange and toward said cover forengagement therewith when a wire gripped by the wings is pulled in awithdrawal direction.

8. The device of claim 5 in which the said wings are prevented fromspreading by lateral engagement with walls of said base and the includedangle between said twisted wings is substantially greater than wherebyattempted withdrawal of a gripped wire causes the wings to grip ittighter.

9. The device of claim 8 in which said cover has a wire inserting holeabove the narrow portion of each slot and an adjacent transverse slotfor the insertion of a releasing blade.

References Cited in the file of this patent UNITED STATES PATENTS2,206,799 Barton July 2, 1940 2,259,740 Del Camp Oct. 21, 1941 2,550,237Franklin Apr. 24, 1951 FOREIGN PATENTS 564,065 Germany Nov. 23, 1932659,316 Great Britain Oct. 25, 1951

